Polymerizing organosilicon compounds with sulfur-containing organo tin catalysts



United States Patent O POLYMEREZING ORGANOSILICON COMPOUNDS WITHSULFUR-QONTAINENG ORGAN O TIN CATALYSTS Ronald O. Hadlock and Martin E.Sorkin, Greensboro, N.C., assignors to Dow Corning Corporation, Midland,Mich., a corporation of Michigan No Drawing. Continuation-impart ofapplication Ser. No. 601,840, Dec. 15, 1966. This application Mar.8,-1968, Ser. No. 711,503

Int. Cl. C08g 31/40; C07f 7/08 US. Cl. 260--46.5 4 Claims ABSTRACT OFTHE DISCLOSURE organosilicon compounds containing the SiOH group arepolymerized with diorgano tin compounds having the configuration ESnSCHCOO- (e.g.

4 9) z 2 4 9] 2) The cured products are superior for releaseapplications.

pounds suffers from several disadvantages. One is the relativeinstability of the compound as shown by loss of activity upon standing,particularly under moist conditions. Then phenomenon is even morepronounced when the catalyst is in the form of an aqueous emulsion. Itis necessary, of course, to employ aqueous emulsions of catalysts withorganosilicon coating compositions which are in emulsion form. Forexample, a wide variety of organosilicon release coatings for paper areapplied from emulsion and thereafter cured.

Under these conditions, it is necessary for the catalyst emulsion to bestable on storage. It is also necessary for the coating bath to remainstable during the coating process when a mixture of the catalystemulsion and the organosilicon emulsion is applied to the paper byvarious mechanical means. This may involve pumping the emulsion andsmearing it on the surface of the paper with coating rolls or a coatingknife, or spraying the emulsion onto the paper through orifices. Thismechanical agitation and stress has a great tendency to break down theemulsion, and particularly to reduce the effectiveness of the catalysts.

The problems encountered with the heretofore employed tin catalysts havebeen solved or greatly reduced by the use of a catalyst hereinafterdescribed.

Another problem which has been found with previously employed organotincompounds lies in the realm of food release. In this applicationsolutions of phenylmethylsiloxane resins are applied to cooking surfacesand there after cured. One type of such resin is particularly suitablefor use on frying pans, baking dishes, and other ovenware. The goal isto provide easy release for all types of foods so as to obviate orreduce to a minimum the use of grease and to make the cleaning of theutensil much easier. It has been found that when the catalystshereinafter described are employed, the release capability of siloxanefilm is greatly enhanced.

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This invention relates to a method of polymerizing organosiliconcompounds 1) containing at least one SiOH group and on the average from0.9 to 3 organic groups attached to the silicon through Si-C linkageswhich comprises contacting said organosilicon compound with (2) acatalyst of the formula R Sn(SCH COOR') in which R is a monovalenthydrocarbon radical and R is an alkyl radical, at a temperaturesuflicient to cause an increase in the molecular weight of theorganosilicon compound.

The catalysts employed herein are useful as polymerization catalysts inwhich the molecular weight of the organosilicon compound is increasedand especially as curing catalysts in which a polyfunctionalorganosilicon compound is rendered insoluble and infusible. Theoperativeness of the compositions of this invention applies to anyorganosilicon compound containing at least one SiOH group. In addition,the organosilicon compound can contain other types of silicon functionalgroups (SiX) which react with water to produce SiOH groups, or whichreact directly with SiOH groups to produce SiO-Si bonds with theelimination of HX.

This means then one can mix the catalyst with a silicon compoundcontaining only SiX groups and then expose the mixture to moisture. Thelatter will hydrolyze the X groups to OH and the latter will becondensed by the catalyst to cause polymerization of the siliconcompound.

As is well known, such X groups include hydrogen; alkoxy groups such asmethoxy, ethoxy and OCH CH OCH acyloxy groups such as acetoxy,propionyloxy and benzoyloxy; ketoxime groups such as -ON=C(CH carbamategroups such as groups of the formula ONY in which Y is a hydrocarbonradical such as methyl, ethyl or phenyl; halogen atoms such as Cl, Brand F; and any other hydrolyzable groups attached to the silicon.

The organosilicon compounds employed herein are those which contain onthe average from 0.9 to 3 organic groups which are attached to thesilicon through SiC linkages (R"). For the purpose of this invention itis immaterial What type of substituent is so attached to the silicon.Thus, the substituent group can be any hydrocarbon. or any substitutedhydrocarbon group. Preferably, the substituents are hydrocarbon groupssuch as aliphatic hydrocarbons, such as methyl, ethyl, octadecyl,myricyl, vinyl, allyl, hexenyl and isopropyl; cycloaliphatic hydrocarbongroups such as cyclohexyl, cyclopentyl, methy1 cyclohexyl, cyclohexenyland methylcyclohexenyl; aromatic hydrocarbon groups such as phenyl,tolyl, xenyl, xylyl and naphthyl; and aralkyl groups such as benzyl,fl-phenylethyl, and p-phenylpropyl.

The preferred substituent groups can also be any halogenated hydrocarbonradical such as chloromethyl, gamma-chloropropyl, bromooctadecyl,chlorophenyl, bromoxenyl, fluorocyclohexyl, chlorobutenyl,a,oc,oc-trifiu010- tolyl, 3,3,3-trifluoropropyl, and C F CH CH Othersubstituted hydrocarbon radicals can be hydrocarbon ether radicals suchas (CH O(CH CH O) CH and (CH OC H ester groups such as --(CH -OOCCH andCH CH COOC H nitrile groups such as -CH2CH2CEN, -(CH CEN and andhydrocarbon groups substituted with amino, amido and sulfide groups. Themost preferred substituents on the silicon are alkyl, vinyl, phenyl andR;CH CH radicals where R is a perfiuoroalkyl radical.

structurally, the organosilicon compounds employed herein can be anycombination of units of the formulae RSiO R" SiO, R" SiO and limitedamounts of SiO units. The organosilicon compounds can also containsilicon atoms which are linked directly to other silicon atoms or arelinked to silicon atoms through divalent hydrocarbon atoms such asmethylene, dimethylene, hexamethylene, phenylene and xylylene orhydrocarbon ether radicals such as C H OC H silazine linkages such H CHsirlisi, SiI ISi and sulfide linkages such as SiSSi.

The organosilicon compound can be contacted with the catalyst of thisinvention at any stage in its degree of polymerization. Thus one cancontact silanols or diols with the tin compound or one can contactsiloxanols having a high degree of polymerization in order to affect thefinal cure of the compositions.

The organo tin compounds employed herein are commercially availablematerials. They can be made by reacting tin oxides of the formula withmercaptides of the formula HSCH COOR. The tin oxide is readily preparedby the hydrolysis of R SnCl which in turn is readily prepared byreacting RMgCl with SnCl For the purpose of this invention R can be anyhydrocarbon radical such as methyl, ethyl, butyl, octyl, octadecyl,myricyl, phenyl, tolyl, vinyl, allyl, benzyl, or xenyl and R can be anyalkyl radical such as methyl, ethyl, Ibutyl, octyl, octadecyl andmyricyl. It is preferred that both R and R be alkyl radicals of at leastfour carbon atoms.

The proportion of catalyst is not critical for carrying out thisinvention. In general, as with any catalyst, one prefers to employ thesmallest amount necessary to cause proper polymerization. Thetemperature of polymerization is not critical and varies widelydepending upon the nature of the organosilicon compound. With somecompounds polymerization will take place at room temperature or below,and with others, elevated temperatures are needed. Also the temperatureemployed varies with the time required for carrying out thepolymerization. Thus, for example, elevated temperatures may be neededto cure a coating in a few seconds, whereas room temperature wouldsuffice if the coating could be cured over a period of 24 hours.

The catalyst of this invention can be used in preparation of laminates,molded articles and in the curing of films and coatings, with eitherresinous, fluid or rubbery compositions.

The following examples are illustrative only and should not be construedas limiting the invention which is properly delineated in the appendedclaims.

EXAMPLE 1 This example illustrates the superior performance of acommercial organosilicon food release composition when catalyzed withdi-N-octyltin-di-iso-octylmercaptoacetate (1) as compared with therelease obtained with other organo tin catalysts. The formulation usedin each test infra was in weight percent as follows:

3.10 of a methylphenylpolysiloxane resin containing 4% by weightsilicon-bonded OH groups and having a phenyl to silicon ratio of 0.53and a total methyl and phenyl to silicon ratio of 1.35,

0.01 monomethylether of dipropylene glycol,

4 0.20 of a hydroxylated dimethylpolysiloxane fluid having 4.2% byweight Si bonded OH, 1.79 methyltriacetoxysilane and 94.90 of1,1,1-trichloroethane.

To various batches of the above formulation was added the followingcatalysts in each case in amount of 1 part by weight tin per 100 partsby weight total organosilicon solids.

( l di-N-octyltin-di-iso-octylmercaptoacetate (2) di-octyltin-di-octoate(3) di-octyltin-di-laurate (4) di-butyltin-di-laurate Each catalyzedformulation was placed in a closed container and stored for the time andat the temperature shown in the tables infra. Each was then applied toan aluminum frypan and allowed to air dry. Eggs were then fried at 275F. in the coated pan without any grease and the number of timessatisfactory release was obtained was recorded.

Three different lost of the phenylmethyl resin was employed and aredesignated I, II and III below.

In this set of experiments the materials were mixed and tested at onceand then aged at 70 F. and tested after the number of times specified.

Ageing time in months Lot II 1 Experiment stopped after releases.

In this set of experiments each sample was aged in the container at thespecified temperature and then checked for egg release as shown above.

Ageing time in months Tempera- Lot 11 Lot 11 Lot III ture F.) 2 3 5 6 45 6 5 6 Measuring food release 15 not a particularly precisedetermination so it is necessary to check a relatively large number ofsamples in order to determine which product is, in fact superior. Thesuperiority of (1) is shown by the fact that it gave superior releasewith respect to all the catalysts in 26 cases, to at least one othercatalyst in 29 cases and was inferior in only 10 cases. Furthermore,catalyst (1) was superior in 9 out of 10 cases upon ageing at 70 F.which is the normal storage conditions for a commercial product.

EXAMPLE 2 The siloxane emulsion had the following composition in weightpercent:

38.800 OH endblocked dimethylpolysiloxane fluid 1.200 methylhydrogenpolysiloxane Organosilicon compound 3) 2 (ICHB) 2 Temperature, C.

l I 4.500 toluene 5 HOSFQSKE 5.500 perchloroethylene 47.077 water(31120111 1.875 polyvinyl alcohol and 30 Mixture of no si-o H and 1.048octylphenyl polyethoxy ethanol (3H3 {a parts by weight of the siloxaneemulsion was mixed l0 with 2.5 parts of the catalyst emulsion and 72.5parts 150 g gggg jfglgfig gfiggf water. The resulting emulsion wasapplied to parchment 20 molpercent onisios/i paper with a glass rod andcured 2 minutes at 250 F. 58 ggfgggi Excellent cure of the siloxane wasobtained as shown by the good release values which remained essentiallycon- 15 stant as the bath aged. gs i g i izgi i r si p n ifiilz io r iih h rs. Release in g. Subsequent adhesion That which iS claimed is;

5 160 90 1. A method of polymerizing organosilicon compounds 5 145 7 1)containing at least one SiOH group and any re- 2 fig maining siliconvalences in said organosilicon com- 6 140 pound being satisfied byradicals selected from the 268 group consisting of silicon-bonded oxygenatoms by a and Johnson surgical adhesive tape to the cured siloxane thasilazane linka e silicombonded Sulfur radicals and measuring the forcerequired to remove the tape from to form the 1i nka e linka e and thesurface bypulling at 180 angle. The tape so removed organic groupsattached to i silicon througgll the was then applied to a steel paneland the force required Sic linkage Selected fr m th group consisting ofto remove the tape is measured. The values above show disilylolkylenedisflylarylene disylhydmcarbon that the tape released easily from thecoated paper and ether linkage monovalent hydrocarbon monovalent that noappreciable siloxane adhered to the tape because halohydrocarijon mon CV31 em hydrocarbon ether of the excellent lq to the Steelnitrile-substituted monovalent hydrocarbon, ester The excellentstability of the emulsion to mechanical Substituted monovalent hdrocarbon and mono working was shown by the fact that the emulsion didnot valent h drocarbon mu gilbstituted :vith an amino gel or oil during6 hours operation on coating rolls at 10 amide i Sulfide f there beingon the average yards per minute. This shows a roll stability of greaterfrom 6 to 3 f id organic groups attached to the than 6 hours EXAMPLE 3silicon which comprises contacting said organo- 40 silicon compound withExcellent cures are obtained when the following cata- (2) a catalyst ofthe formula R Sn(SCH COOR') in lysts are used with the composition ofclaim 1. which R is a monovalent hydrocarbon radical and R is an alkylradical, at a temperature sufiicient to (ciHg)(CH2 CH)SMSCHZCOOCZDHm]2cause an increase in the molecular weight of the (C2H5)2Sn [scHzcoocsHn]2 organosilicon compound. 2?g g gggig gfgggg g 2. The method of claim 1in which the organic groups SMSCIFI 6 attached to the silicon areselected from the group conh H sisting of alkyl, phenyl, vinyl and R CHCH where 4 9 2 2 8 17 2 R is a perfiuoroalkyl radical, and R and R arealkyl naphthyubutyl) SH[SCH2COOC6H13]2 radicals of at least 4 carbonatoms (C H CH CH Sn[SCH COOC H 6 5 2 2 2 3. The method of claim 1 inwhich (2) is di-N-octyltin- EXAM 4 di-iso-octylmercaptoacetate.Polymerization occurs when the following organo- The method of claim 2in which (2) is di'N'octylfin' silicon compounds are mixed with thecatalyst of Example 7 dllso'octyl mercaptoacetate' 1 and heated as shownbelow. 59 References Cited Temperature, G. Organosilicon compound UNITEDSTATES PATENTS ICHZCHZCFB 2,842,516 7/1958 Nitzshe et a1. 26037 30-(fixture of ]H d e fler CH3 DONALD E. GZAJA, Primary Examiner 150Ethylpolysilicatfi s i)2 )2 I. M ARQUIS Assistant Examiner US. Cl. X.R.

(30135 Mixture 0f Ho[?i0 H and

